The present invention relates to assemblies and devices for the brewing of a beverage; the invention may, for example, be used in coin operated vending machines and the like. The invention particulary relates to beverages brewed from an aqueous medium and a particulate beverage material (for example, from, hot water and a coffee material, a tea material or the like).
For vending machines, it is desirable, from the point of view of the user, to be able to obtain a (acceptable) cup of beverage in as short a period of time as possible. From the point of view of the operator of the vending machine it is desirable to be able separate a maximum amount of beverage from the particulate beverage material; in this latter respect it is also desirable to have as dry a residue as possible in order to facilitate disposal of the residue.
The brew period for the extraction of an acceptable amount of solubles under ambient pressure conditions, may be reduced by increasing the amount of coffee grounds used per cup; this tactic however, increases the unit cost of the beverage product.
A number of coffee machines are known which employ a piston/cylinder combination for brewing coffee. At the end of each brew cycle, the coffee beverage, prior to discharge, is forced to pass through a filter, the ground coffee residue collected by the filter being thereafter separated from the piston/cylinder combination prior to the next brew cycyle.
Thus U.S. Pat. No. 3,565,641 teaches a piston/cylinder combination whereby a coffee beverage may be brewed in cup size amounts within a relatively brief period of time by forcing air through the mixture of hot water and beverage material and then filtering the obtained coffee beverage. Such air induced agitation improves considerably the brewing (leaching) process; it promotes and accelerates the thorough wetting of each of the particles of coffee by the hot water; and the agitation changes the water actually in contact with the coffee grounds so as to enhance the rate at which beverage (coffee) solubles dissolve. The brew-chamber of this reference is provided with a floor wall which is permeable to liquid and air but impermeable to the bulk of the insoluble coffee grounds; this floor wall also divides the brew-chamber from a piston-chamber. A piston is disposed in the piston-chamber for inducing a positive pressure (on the upward stroke) and a negative pressure (on the downward stroke). The piston/cylinder combination is configured such that during the upward stroke, the piston forces air trapped in the piston-chamber between the piston and the floor wall to pass through the floor wall into the the brew chamber so as to agitate the , liquid/solids mixture in the brew chamber. On the downward stroke away from the floor wall, beverage is pulled or sucked through the floor wall into the piston-chamber between the piston and the floor wall. An outlet is provided in the wall of the piston-chamber, spaced from the floor wall such that at the end of the downward stroke the coffee beverage can escape the piston-chamber by gravity into a waiting cup. Means are also provided for removing the waste coffee ground from the floor wall by replacing the used filter (with the grounds deposited thereon) with a fresh filter before each new brew cycle.
An alternate piston/cylinder combination is taught in U.S. Pat. No. 3,369,478; in this reference a permanent type filter is used. The piston/cylinder combination taught is such that the filter is mounted on the end of the piston, the upper surface of the filter being exposed after the brewing cycle for scraping away waste coffee grounds by scraper means. A small cavity is defined between the filter and the body of the piston and an opening through the piston body is included which communicates with the cavity. During the upward stroke of the piston, the brewing chamber is sealed off and contains in addition to the brewing mixture a cushion or layer of trapped air. The upward compression stroke of the piston effects discharge of the beverage and trapped air through the filter into the cavity for evacuation through the opening; the air is passed through the waste ground coffee for the purpose of effecting drying of this residue.
A number of drawbacks and limitations are associated with piston/cylinder combinations used for coffee brewers, namely:
A relatively large number of moving parts are associated with the pumping function. Accordingly, close attention must be paid to the repair and upkeep of the mechanism; more particularly, should the suction and compression characteristic of the system fall below that which is required, an expert repair person is needed in order to dismantle and rebuild the mechanism to replace or repair the piston/cylinder combination.
The maximum amount of coffee which may be produced by a piston/cylinder combination is limited by the volume displaceable during the piston stroke. In order to be able to deliver a larger maximum volume of coffee, the structure of the piston/cylinder combination must be altered so as to increase the upper limit of the pumping volume e.g. both the piston and cylinder may have to be replaced by correspondingly larger diameter or longer stroke units, the motor mechanism driving the piston including the piston arm may have to be replaced by a larger unit, etc. . . If significant replacements must be made, these can be burdensome to effect and can result in an undesirable increase in the size and weight of the apparatus. Morever, if the apparatus is intended to deliver a range of coffee volumes, increasing the size of the piston/cylinder combination may accentuate other drawbacks of such systems in relation to product taste, to the brewing temperature as well as the temperature of the final product.
The pumping mechanism has a relatively large number of parts such as the cylinder side walls, the piston head etc. which come into direct contact with the beverage; such contact can affect the final temperature of the product. The many parts of the mechanism can act as a heat sink with the undesirable side effect of robbing heat from the beverage during brewing, resulting in less efficient extraction of coffee solubles, i.e. extraction occurs better at higher water temperatures. This temperature effect will be greater, if the apparatus is intended to deliver a coffee volume which is smaller than the maximum pumping volume, i.e. the smaller volume of coffee to be produced will loose more relative heat than the larger volume.
As mentioned above, the maximum amount of coffee which may be produced by a piston/cylinder combination is limited by the volume displaceable during the piston stroke. However, for known devices, such as those following the teachings of U.S. Pat. No. 3,565,641, the brew vessel may provide a further limitation with respect to the maximum amount of coffee which may be produced. During the injection of air to agitate the brew mix, a significant amount of frothing or foaming may occur; the foam so produced, can, (if no special precautions are taken such as limiting the amount of brew mix and/or inserting foam suppression baffles in the brew vessel) overflow from the brew vessel and thus be lost as spillage.
for known devices such as those following the teachings of U.S. Pat. No. 3,565,641 a significant amount of fluid can remain in the piston-chamber (e.g. for an initial water input of 150 cc about 15 cc can remain in the piston chamber). A subsequent cup of coffee can thus be contaminated by this residual liquid, i.e. the residual liquid can lower the temperature of the beverage served and can distort its taste.
for known devices such as those following the teachings of U.S. Pat. No. 3,565,641 the coffee residue is relatively moist; for known devices such as those following the teachings of U.S. Pat. No. 3,369,478 the compressed air will tend to wedge particles into the openings of the permanent filter.
Accordingly, it would be advatageous to have an assembly for a brewing apparatus having a mechanically simple brew/pump mechanism with few moving parts and which can be relatively easily repaired or replaced.
It would be advatageous to have an assembly for a brewing apparatus having a mechanically simple brew/pump mechanism for providing a relatively small sized apparatus able to dispense relatively large single servings of a beverage such as coffee as well as relatively small servings (e.g. serving any amounts variable in size between about 4 to about 16 ounces).
It would be advantageous to have a mechanically simple brew/pump assembly for a brewing apparatus, the assembly having a reduced number of brew/pump elements, so as to limit or reduce beverage contact therewith as well as heat transfer during brewing and dispensing of the beverage.
It would be advantageous to have a mechanically simple brew/pump assembly for a brewing apparatus which provides for a positive and total displacement of beverage to a cup.
It would be advantageous to have a mechanically simple brew/pump assembly for a brewing apparatus which provides for back purge of air through the grounds residue after the beverage has been dispensed and which faclitates drying of the grounds residue and the loosening therof from the filter to facilitate removal from the filter or filter support means.
It would be advantageous to have a mechanically simple brew/pump assembly for a brewing apparatus, the assembly having a simple and relatively compact mechanism for suppressing splillage due to foaming during the injection of air into a brew vessel.